Re: HF amp kits

The Linear Amp kits seem to need a fair amount of drive. I've been
idly thinking about a linear that would allow me to drive it with
my barefoot K2 and get 600-800 watts out for CW.

I've been told that such things were "common" in the 70s. One description
I was given is

two stages, with a pair of 6CL6 pentodes in class A passive grids,
driving a pair of surplus 4CX250Bs in AB1,a very common design.
0.1W in gives 650W out.

which sort of means something to me, but will certainly start many
evenings of study.

If this was "common", it seems that there should be articles. I haven't
had much luck finding one (there's an article from 1959 that uses
a single 4CX250B). So, how about it, you guys who were there then? :-)

Re: HF amp kits

A pair of tetrodes or pentodes, grid driven in AB1 need little drive,
so the 12 watts from a K2 may be sufficient for driving something like
a 4CX800. You may need switched tuned inputs instead of passive grid to
drive it with 12W. I think most amplifiers on the market are class AB2
(usually grounded grid), which need plenty of drive. The drawback in
using tetrodes or pentodes in AB1 is the requirement of a regulated high
voltage for the screen grids and the amplifier would probably need
neutralizing also, especially if not operating in passive grid. Most
available tetrodes are ceramic types, so a blower would be necessary too
As you intend only running CW, it may be worthwhile investigating class
E amplifiers which would present you with more modern obstacles to
overcome :-)
73, Dave G3VGR
K2 #4783

Chris Kantarjiev wrote:

> [warning thread drift]
>
> The Linear Amp kits seem to need a fair amount of drive. I've been
> idly thinking about a linear that would allow me to drive it with
> my barefoot K2 and get 600-800 watts out for CW.
>
> I've been told that such things were "common" in the 70s. One description
> I was given is
>
> two stages, with a pair of 6CL6 pentodes in class A passive grids,
> driving a pair of surplus 4CX250Bs in AB1,a very common design.
> 0.1W in gives 650W out.
>
> which sort of means something to me, but will certainly start many
> evenings of study.
>
> If this was "common", it seems that there should be articles. I haven't
> had much luck finding one (there's an article from 1959 that uses
> a single 4CX250B). So, how about it, you guys who were there then? :-)
>
> 73 de chris K6DBG
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft>
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Re: HF amp kits

With barefoot K2 you don't need two stages to get 600-800 watts out. For
instance 4CX800 is happy grid driven with 10 watts. Unfortunately most HB PA
articles now are in Russian. However I could help with the translation, if
needed. Having only smaller tubes in my junk box, I am working now on a grid
driven 4xEL509, delivering 400-500 watts. PA0FRI have a great web site for
the amp home brewers. See http://www.xs4all.nl/~pa0fri/Lineairs/Lineairs.htm

73, Val LZ1VB

> The Linear Amp kits seem to need a fair amount of drive. I've been
> idly thinking about a linear that would allow me to drive it with
> my barefoot K2 and get 600-800 watts out for CW.
>
> I've been told that such things were "common" in the 70s. One description
> I was given is
>
> two stages, with a pair of 6CL6 pentodes in class A passive grids,
> driving a pair of surplus 4CX250Bs in AB1,a very common design.
> 0.1W in gives 650W out.
>
> which sort of means something to me, but will certainly start many
> evenings of study.
>
> If this was "common", it seems that there should be articles. I haven't
> had much luck finding one (there's an article from 1959 that uses
> a single 4CX250B). So, how about it, you guys who were there then? :-)
>
> 73 de chris K6DBG

Re: HF amp kits

Any class AB1 amplifier requires no power to the grid to develop full
output. However, the proper voltage swing at the grid is required. If
you use a tetrode, a link coupled parallel tuned circuit in the grid
will usually provide the required voltage swing.

The downside of such designs is that the grid circuit must be isolated
from the plate circuit and a stiff screen voltage supply (preferably
regulated) is needed. Neutralization is a must and band switching can
be a problem with multiple tuned circuits to switch coupled with the
isolation required.

Since the 'swamped grid' amplifiers and grounded grid designs are not as
prone to oscillation and are relatively easy to 'tame', you will find
more published designs for these type amplifiers and few for the tuned
input designs.

Take a look at some of the single band amplifier designs which avoid the
band switching complexity and you will likely find what you are looking for.

73,
Don W3FPR

Chris Kantarjiev wrote:

> [warning thread drift]
>
> The Linear Amp kits seem to need a fair amount of drive. I've been
> idly thinking about a linear that would allow me to drive it with
> my barefoot K2 and get 600-800 watts out for CW.
>
> I've been told that such things were "common" in the 70s. One description
> I was given is
>
> two stages, with a pair of 6CL6 pentodes in class A passive grids,
> driving a pair of surplus 4CX250Bs in AB1,a very common design.
> 0.1W in gives 650W out.
>
> which sort of means something to me, but will certainly start many
> evenings of study.
>
> If this was "common", it seems that there should be articles. I haven't
> had much luck finding one (there's an article from 1959 that uses
> a single 4CX250B). So, how about it, you guys who were there then? :-)
>
> 73 de chris K6DBG

RE: HF amp kits

I have a pair of 4cx250b/4x150a tubes as modulators
for my 813 AM transmitter.
Great tubes, you can go from 1000 volts on the plate to 2000
volts in AB1 without bias or screen voltage changes.
900 watts of audio out, the same for CW I suppose.
That's at 2000 volts 500ma.
They take zero driving power in AB1, just voltage, so a
typical tuned grid input would work.

The downside of the 4cx250b type tubes is you need a
blower and the special sockets, and regulated screen voltage
for low distortion on voice.
Not sure if you need to regulate the voltage for CW...

Many tubes take low driving power if you do the tuned grid input.
Its another thing to tune, but not really hard to do, a tapped coil
on a ceramic form with a link at the bottom, or separate coils
of B+W coil stock switched in gets the drive for a pair of 813's
down to about 15 watts for over 600 watts out in class C.
My pair of 813's is not neutralized and seems to have no problems
working from 1.8 to 30 mc.
I set it up so it can be class c or AB2, all parameters are metered
and adjustable.

> [warning thread drift]
>
> The Linear Amp kits seem to need a fair amount of drive. I've been
> idly thinking about a linear that would allow me to drive it with
> my barefoot K2 and get 600-800 watts out for CW.
>
> I've been told that such things were "common" in the 70s. One
> description
> I was given is
>
> two stages, with a pair of 6CL6 pentodes in class A passive grids,
> driving a pair of surplus 4CX250Bs in AB1,a very common design.
> 0.1W in gives 650W out.
>
> which sort of means something to me, but will certainly start many
> evenings of study.
>
> If this was "common", it seems that there should be articles.
> I haven't
> had much luck finding one (there's an article from 1959 that uses
> a single 4CX250B). So, how about it, you guys who were there then? :-)
>
> 73 de chris K6DBG
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft>
> Help: http://mailman.qth.net/subscribers.htm> Elecraft web page: http://www.elecraft.com>

Re: HF amp kits

Chris Kantarjiev wrote:
> [warning thread drift]
>
> The Linear Amp kits seem to need a fair amount of drive. I've been
> idly thinking about a linear that would allow me to drive it with
> my barefoot K2 and get 600-800 watts out for CW.

Didn't there used to be a Part 97 gain limit of 10dB for RF amps? Is it
still there? I'd go check myself but I've been reading the regs trying
to sort out RM11306 for comments, and my eyes are now legally crossed
from all the Fed-Speak.

Re: HF amp kits

On Apr 5, 2007, at 9:17 AM, Fred Jensen wrote:

> Chris Kantarjiev wrote:
>> [warning thread drift]
>> The Linear Amp kits seem to need a fair amount of drive. I've been
>> idly thinking about a linear that would allow me to drive it with
>> my barefoot K2 and get 600-800 watts out for CW.
>
> Didn't there used to be a Part 97 gain limit of 10dB for RF amps?
> Is it still there? I'd go check myself but I've been reading the
> regs trying to sort out RM11306 for comments, and my eyes are now
> legally crossed from all the Fed-Speak.
>

The limit is 15 dB and is still in the requirements despite the
recent loosening of Part 97. That should give something over 400
watts when driven by a K2. I don't recall whether the "easily-
modifiable" rule is still there, so it may be possible to have an amp
with an attenuator on the front-end (I heard that one of the Tokyo
High Power amps does this, but haven't verified that).

Re: HF amp kits

The 15 db rule applies only to manufactured for sale amplifiers. It
does not apply to amplifiers that an individual ham builds for him or
herself, particularly when a a kit is not involved.. Section 97.317 of
the rules, which is where the 15 db rule appears, applies to the
certification of external RF power amplifiers that a manufacturer offers
for sale. Home-made amplifiers do not require certification. They must
still meet some standards, such as those involving purity of emissions
(harmonics, for example) and of course must not be operated above 1500
watts PEP, but that's pretty much it.

I am unsure of how the rule applies to kits, but I think they would be
considered a "manufactured product" if all the parts needed to complete
the amplifier are contained, in the kit. If, however, a "kit" contained
only some of the parts, and could not in itself be assembled into a
working amplifier without adding extra parts, then the certification
rule probably would not apply.

It would be perfectly legal for a ham to build a home-brew grid-driven
amplifier that could take the 10 watt signal from his K2 and boost it
to 1500 watts output. Such an amplifier would have (roughly) 22 db of
gain. A pair of 4CX800 tubes could accomplish this, I think.
Remember also that the old Johnson Thunderbolt could be operated in
grid-driven mode, and it had (still has, if you can find one) similar
performance, using a pair of 4-400 tubes.

- Jim, KL7CC

>
>> Chris Kantarjiev wrote:
>>
>>>
>>> The Linear Amp kits seem to need a fair amount of drive. I've been
>>> idly thinking about a linear that would allow me to drive it with
>>> my barefoot K2 and get 600-800 watts out for CW.
>>
>
> The limit is 15 dB and is still in the requirements despite the
> recent loosening of Part 97. That should give something over 400
> watts when driven by a K2. I don't recall whether the "easily-
> modifiable" rule is still there, so it may be possible to have an amp
> with an attenuator on the front-end (I heard that one of the Tokyo
> High Power amps does this, but haven't verified that).
>
> 73, Bob N7XY
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]> You must be a subscriber to post to the list.
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> http://mailman.qth.net/mailman/listinfo/elecraft> Help: http://mailman.qth.net/subscribers.htm> Elecraft web page: http://www.elecraft.com>
>

Re: HF amp kits

Not to offend the QRP purists in the group, but I think an modest amplifier kit would be spectacular....if you could keep the kit down below a a grand. I looked at the one from the UK and I felt that it was pretty easy to build...especially for those of us who built amps before from scratch. AH yes, the good old days.....

But, there are some liabilities....and I am no sure that a company wants to get bonded for those people who die because they did not understand the ramifications of 1500 to 2500 volts. I wonder how Heath handled that?

Anyway, using a grid driven tetrode or triode would be a task to tame, but it could be done...but I would rather not. Therefore, you would have to go to the GG and that means drive. You would have to have at least 50 watts to get any kind of output.

I like the idea....I would build one in a minute....but there are complications

Lee - K0WA

In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense devine?
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> The 15 db rule applies only to manufactured for sale amplifiers. It
> does not apply to amplifiers that an individual ham builds for him or
> herself, particularly when a a kit is not involved.. Section 97.317 of
> the rules, which is where the 15 db rule appears, applies to the
> certification of external RF power amplifiers that a manufacturer offers
> for sale. Home-made amplifiers do not require certification. They must
> still meet some standards, such as those involving purity of emissions
> (harmonics, for example) and of course must not be operated above 1500
> watts PEP, but that's pretty much it.
>
> I am unsure of how the rule applies to kits, but I think they would be
> considered a "manufactured product" if all the parts needed to complete
> the amplifier are contained, in the kit. If, however, a "kit" contained
> only some of the parts, and could not in itself be assembled into a
> working amplifier without adding extra parts, then the certification
> rule probably would not apply.
>
> It would be perfectly legal for a ham to build a home-brew grid-driven
> amplifier that could take the 10 watt signal from his K2 and boost it
> to 1500 watts output. Such an amplifier would have (roughly) 22 db of
> gain. A pair of 4CX800 tubes could accomplish this, I think.
> Remember also that the old Johnson Thunderbolt could be operated in
> grid-driven mode, and it had (still has, if you can find one) similar
> performance, using a pair of 4-400 tubes.
>
>
> - Jim, KL7CC
>
>
>
>
>>
>>> Chris Kantarjiev wrote:
>>>
>>>>
>>>> The Linear Amp kits seem to need a fair amount of drive. I've been
>>>> idly thinking about a linear that would allow me to drive it with
>>>> my barefoot K2 and get 600-800 watts out for CW.
>>>
>>
>> The limit is 15 dB and is still in the requirements despite the
>> recent loosening of Part 97. That should give something over 400
>> watts when driven by a K2. I don't recall whether the "easily-
>> modifiable" rule is still there, so it may be possible to have an amp
>> with an attenuator on the front-end (I heard that one of the Tokyo
>> High Power amps does this, but haven't verified that).
>>
>> 73, Bob N7XY
>>
>>
>> _______________________________________________
>> Elecraft mailing list
>> Post to: [hidden email]>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>> http://mailman.qth.net/mailman/listinfo/elecraft Help:
>> http://mailman.qth.net/subscribers.htm>> Elecraft web page: http://www.elecraft.com>>
>>
> _______________________________________________
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> Post to: [hidden email]> You must be a subscriber to post to the list.
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> http://mailman.qth.net/mailman/listinfo/elecraft> Help: http://mailman.qth.net/subscribers.htm> Elecraft web page: http://www.elecraft.com>

Re: HF amp kits

I have been a ham for 43 plus years (12/23/63) and up to now have not
heard of any such limitation.

Jozef WB2MIC

David Wilburn wrote:

> Just working from memory here, but wasn't there also a limit that the
> amateur could only build one such amp a year?
>
> David Wilburn
> [hidden email]> K4DGW
> K2 #5982
>
>
> Jim Wiley wrote:
>> The 15 db rule applies only to manufactured for sale amplifiers. It
>> does not apply to amplifiers that an individual ham builds for him or
>> herself, particularly when a a kit is not involved.. Section 97.317
>> of the rules, which is where the 15 db rule appears, applies to the
>> certification of external RF power amplifiers that a manufacturer
>> offers for sale. Home-made amplifiers do not require certification.
>> They must still meet some standards, such as those involving purity
>> of emissions (harmonics, for example) and of course must not be
>> operated above 1500 watts PEP, but that's pretty much it.
>>
>> I am unsure of how the rule applies to kits, but I think they would
>> be considered a "manufactured product" if all the parts needed to
>> complete the amplifier are contained, in the kit. If, however, a
>> "kit" contained only some of the parts, and could not in itself be
>> assembled into a working amplifier without adding extra parts, then
>> the certification rule probably would not apply.
>>
>> It would be perfectly legal for a ham to build a home-brew
>> grid-driven amplifier that could take the 10 watt signal from his
>> K2 and boost it to 1500 watts output. Such an amplifier would have
>> (roughly) 22 db of gain. A pair of 4CX800 tubes could accomplish
>> this, I think. Remember also that the old Johnson Thunderbolt could
>> be operated in grid-driven mode, and it had (still has, if you can
>> find one) similar performance, using a pair of 4-400 tubes.
>>
>>
>> - Jim, KL7CC
>>
>>
>>
>>
>>>
>>>> Chris Kantarjiev wrote:
>>>>
>>>>>
>>>>> The Linear Amp kits seem to need a fair amount of drive. I've been
>>>>> idly thinking about a linear that would allow me to drive it with
>>>>> my barefoot K2 and get 600-800 watts out for CW.
>>>>
>>>
>>> The limit is 15 dB and is still in the requirements despite the
>>> recent loosening of Part 97. That should give something over 400
>>> watts when driven by a K2. I don't recall whether the "easily-
>>> modifiable" rule is still there, so it may be possible to have an
>>> amp with an attenuator on the front-end (I heard that one of the
>>> Tokyo High Power amps does this, but haven't verified that).
>>>
>>> 73, Bob N7XY
>>>
>>>
>>> _______________________________________________
>>> Elecraft mailing list
>>> Post to: [hidden email]>>> You must be a subscriber to post to the list.
>>> Subscriber Info (Addr. Change, sub, unsub etc.):
>>> http://mailman.qth.net/mailman/listinfo/elecraft Help:
>>> http://mailman.qth.net/subscribers.htm>>> Elecraft web page: http://www.elecraft.com>>>
>>>
>> _______________________________________________
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>> Post to: [hidden email]>> You must be a subscriber to post to the list.
>> Subscriber Info (Addr. Change, sub, unsub etc.):
>> http://mailman.qth.net/mailman/listinfo/elecraft Help:
>> http://mailman.qth.net/subscribers.htm>> Elecraft web page: http://www.elecraft.com>>
> _______________________________________________
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> http://mailman.qth.net/mailman/listinfo/elecraft> Help: http://mailman.qth.net/subscribers.htm> Elecraft web page: http://www.elecraft.com>

Re: HF amp kits

"No more than 1 unit of 1 model of an external RF power amplifier capable of
operation below 144 MHz may be constructed or modified during any calendar
year by an amateur operator for use at a station without a grant of
certification. No amplifier capable of operation below 144 MHz may be constructed or
modified by an amateur operator without a grant of certification from the FCC"

But that's an old rule. It has been removed from Part 97 by FCC.

The intent of the rule was to prevent manufacturers from getting around the
gain-and-frequency regs by getting an amateur license and claiming the amateur
exemption.

> I have been a ham for 43 plus years (12/23/63) and up to now have not
> heard of any such limitation.
>
> Jozef WB2MIC
>
> David Wilburn wrote:
> > Just working from memory here, but wasn't there also a limit that the
> > amateur could only build one such amp a year?
> >
> > David Wilburn
> > [hidden email]> > K4DGW
>

Re: HF amp kits

I built an HF amplifier kit a couple of years ago. The HF Packer amplifier.
It was around $125. All the parts were there and some things have to be
done by the builder that normally are "pre fabbed". Drilling and tapping
holes, placing parts in enclosures accurately.

The amplifier is fairly small and uses two low priced MOS Power FET
transistors. With about 2-3 watts of drive it will produce 35-40 watts of
output. Very nice filtering arrangement on the output, switchable froom
160-10 meters. Has an RF actuated changeover relay system and it is linear
for SSB use. My K1 drives it easily and quite well.

> Just working from memory here, but wasn't there also a limit that the
> amateur could only build one such amp a year?
>
> David Wilburn
> [hidden email]> K4DGW
> K2 #5982
>
>
> Jim Wiley wrote:
>> The 15 db rule applies only to manufactured for sale amplifiers. It does
>> not apply to amplifiers that an individual ham builds for him or herself,
>> particularly when a a kit is not involved.. Section 97.317 of the rules,
>> which is where the 15 db rule appears, applies to the certification of
>> external RF power amplifiers that a manufacturer offers for sale.
>> Home-made amplifiers do not require certification. They must still meet
>> some standards, such as those involving purity of emissions (harmonics,
>> for example) and of course must not be operated above 1500 watts PEP, but
>> that's pretty much it.
>>
>> I am unsure of how the rule applies to kits, but I think they would be
>> considered a "manufactured product" if all the parts needed to complete
>> the amplifier are contained, in the kit. If, however, a "kit" contained
>> only some of the parts, and could not in itself be assembled into a
>> working amplifier without adding extra parts, then the certification rule
>> probably would not apply.
>>
>> It would be perfectly legal for a ham to build a home-brew grid-driven
>> amplifier that could take the 10 watt signal from his K2 and boost it
>> to 1500 watts output. Such an amplifier would have (roughly) 22 db of
>> gain. A pair of 4CX800 tubes could accomplish this, I think. Remember
>> also that the old Johnson Thunderbolt could be operated in grid-driven
>> mode, and it had (still has, if you can find one) similar performance,
>> using a pair of 4-400 tubes.
>>
>>
>> - Jim, KL7CC
>>
>>
>>
>>
>>>
>>>> Chris Kantarjiev wrote:
>>>>
>>>>>
>>>>> The Linear Amp kits seem to need a fair amount of drive. I've been
>>>>> idly thinking about a linear that would allow me to drive it with
>>>>> my barefoot K2 and get 600-800 watts out for CW.
>>>>
>>>
>>> The limit is 15 dB and is still in the requirements despite the recent
>>> loosening of Part 97. That should give something over 400 watts when
>>> driven by a K2. I don't recall whether the "easily- modifiable" rule is
>>> still there, so it may be possible to have an amp with an attenuator on
>>> the front-end (I heard that one of the Tokyo High Power amps does this,
>>> but haven't verified that).
>>>
>>> 73, Bob N7XY
>>>
>>>
>>> _______________________________________________
>>> Elecraft mailing list
>>> Post to: [hidden email]>>> You must be a subscriber to post to the list.
>>> Subscriber Info (Addr. Change, sub, unsub etc.):
>>> http://mailman.qth.net/mailman/listinfo/elecraft Help:
>>> http://mailman.qth.net/subscribers.htm>>> Elecraft web page: http://www.elecraft.com>>>
>>>
>> _______________________________________________
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>> Subscriber Info (Addr. Change, sub, unsub etc.):
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> _______________________________________________
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>
>
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> 12:48 PM
>
>

Re: HF amp kits

G1F02 (B) [97.315a]
Without a grant of FCC certification, how many external RF
amplifiers of a given design capable of operation below 144
MHz may you build or modify in one calendar year?
A. None
B. 1
C. 5
D. 10

> I have been a ham for 43 plus years (12/23/63) and up to now have not
> heard of any such limitation.
>
> Jozef WB2MIC
>
> David Wilburn wrote:
>> Just working from memory here, but wasn't there also a limit that the
>> amateur could only build one such amp a year?
>>
>> David Wilburn
>> [hidden email]>> K4DGW
>> K2 #5982
>>
>>
>> Jim Wiley wrote:
>>> The 15 db rule applies only to manufactured for sale amplifiers. It
>>> does not apply to amplifiers that an individual ham builds for him or
>>> herself, particularly when a a kit is not involved.. Section 97.317
>>> of the rules, which is where the 15 db rule appears, applies to the
>>> certification of external RF power amplifiers that a manufacturer
>>> offers for sale. Home-made amplifiers do not require certification.
>>> They must still meet some standards, such as those involving purity
>>> of emissions (harmonics, for example) and of course must not be
>>> operated above 1500 watts PEP, but that's pretty much it.
>>>
>>> I am unsure of how the rule applies to kits, but I think they would
>>> be considered a "manufactured product" if all the parts needed to
>>> complete the amplifier are contained, in the kit. If, however, a
>>> "kit" contained only some of the parts, and could not in itself be
>>> assembled into a working amplifier without adding extra parts, then
>>> the certification rule probably would not apply.
>>>
>>> It would be perfectly legal for a ham to build a home-brew
>>> grid-driven amplifier that could take the 10 watt signal from his
>>> K2 and boost it to 1500 watts output. Such an amplifier would have
>>> (roughly) 22 db of gain. A pair of 4CX800 tubes could accomplish
>>> this, I think. Remember also that the old Johnson Thunderbolt could
>>> be operated in grid-driven mode, and it had (still has, if you can
>>> find one) similar performance, using a pair of 4-400 tubes.
>>>
>>>
>>> - Jim, KL7CC
>>>
>>>
>>>
>>>
>>>>
>>>>> Chris Kantarjiev wrote:
>>>>>
>>>>>>
>>>>>> The Linear Amp kits seem to need a fair amount of drive. I've been
>>>>>> idly thinking about a linear that would allow me to drive it with
>>>>>> my barefoot K2 and get 600-800 watts out for CW.
>>>>>
>>>>
>>>> The limit is 15 dB and is still in the requirements despite the
>>>> recent loosening of Part 97. That should give something over 400
>>>> watts when driven by a K2. I don't recall whether the "easily-
>>>> modifiable" rule is still there, so it may be possible to have an
>>>> amp with an attenuator on the front-end (I heard that one of the
>>>> Tokyo High Power amps does this, but haven't verified that).
>>>>
>>>> 73, Bob N7XY
>>>>
>>>>
>>>> _______________________________________________
>>>> Elecraft mailing list
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>

Re: HF amp kits

> From the general class question pool.
>
> G1F02 (B) [97.315a]
> Without a grant of FCC certification, how many external RF
> amplifiers of a given design capable of operation below 144
> MHz may you build or modify in one calendar year?
> A. None
> B. 1
> C. 5
> D. 10
>
>
> Here is the ARRL link to the question pool.
> http://www.arrl.org/arrlvec/el3-release-12-1-03.txt>
> David Wilburn
> [hidden email]> K4DGW
> K2 #5982
>
>
> Jozef Hand-Boniakowski wrote:
>> I have been a ham for 43 plus years (12/23/63) and up to now have not
>> heard of any such limitation.
>>
>> Jozef WB2MIC
>>
>> David Wilburn wrote:
>>> Just working from memory here, but wasn't there also a limit that the
>>> amateur could only build one such amp a year?
>>>
>>> David Wilburn
>>> [hidden email]>>> K4DGW
>>> K2 #5982
>>>
>>>
>>> Jim Wiley wrote:
>>>> The 15 db rule applies only to manufactured for sale amplifiers. It
>>>> does not apply to amplifiers that an individual ham builds for him
>>>> or herself, particularly when a a kit is not involved.. Section
>>>> 97.317 of the rules, which is where the 15 db rule appears, applies
>>>> to the certification of external RF power amplifiers that a
>>>> manufacturer offers for sale. Home-made amplifiers do not require
>>>> certification. They must still meet some standards, such as those
>>>> involving purity of emissions (harmonics, for example) and of course
>>>> must not be operated above 1500 watts PEP, but that's pretty much it.
>>>>
>>>> I am unsure of how the rule applies to kits, but I think they would
>>>> be considered a "manufactured product" if all the parts needed to
>>>> complete the amplifier are contained, in the kit. If, however, a
>>>> "kit" contained only some of the parts, and could not in itself be
>>>> assembled into a working amplifier without adding extra parts, then
>>>> the certification rule probably would not apply.
>>>>
>>>> It would be perfectly legal for a ham to build a home-brew
>>>> grid-driven amplifier that could take the 10 watt signal from his
>>>> K2 and boost it to 1500 watts output. Such an amplifier would have
>>>> (roughly) 22 db of gain. A pair of 4CX800 tubes could accomplish
>>>> this, I think. Remember also that the old Johnson Thunderbolt
>>>> could be operated in grid-driven mode, and it had (still has, if you
>>>> can find one) similar performance, using a pair of 4-400 tubes.
>>>>
>>>>
>>>> - Jim, KL7CC
>>>>
>>>>
>>>>
>>>>
>>>>>
>>>>>> Chris Kantarjiev wrote:
>>>>>>
>>>>>>>
>>>>>>> The Linear Amp kits seem to need a fair amount of drive. I've been
>>>>>>> idly thinking about a linear that would allow me to drive it with
>>>>>>> my barefoot K2 and get 600-800 watts out for CW.
>>>>>>
>>>>>
>>>>> The limit is 15 dB and is still in the requirements despite the
>>>>> recent loosening of Part 97. That should give something over 400
>>>>> watts when driven by a K2. I don't recall whether the "easily-
>>>>> modifiable" rule is still there, so it may be possible to have an
>>>>> amp with an attenuator on the front-end (I heard that one of the
>>>>> Tokyo High Power amps does this, but haven't verified that).
>>>>>
>>>>> 73, Bob N7XY
>>>>>
>>>>>
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>>>>>
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>>
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RE: HF amp kits

If someone were to ask me what I considered a "modest" amplifier, I'd say it
was the KPA100.

I look for a 10 dB difference to be worth the effort, time and cost in real
communications ability. After all a 10:1 power difference is less than two
S-units on most meters. To me it's hardly worth the time and effort to go
after less than that, so with 100 watts at my fingertips I'd hardly consider
going for much less than 1,000 watts at the "next step" up.

Not to offend the QRP purists in the group, but I think an modest amplifier
kit would be spectacular....if you could keep the kit down below a a grand.
I looked at the one from the UK and I felt that it was pretty easy to
build...especially for those of us who built amps before from scratch. AH
yes, the good old days.....

But, there are some liabilities....and I am no sure that a company wants to
get bonded for those people who die because they did not understand the
ramifications of 1500 to 2500 volts. I wonder how Heath handled that?

Anyway, using a grid driven tetrode or triode would be a task to tame, but
it could be done...but I would rather not. Therefore, you would have to go
to the GG and that means drive. You would have to have at least 50 watts to
get any kind of output.

I like the idea....I would build one in a minute....but there are
complications

RE: HF amp kits

(a) No more than 1 unit of 1 model of
an external RF power amplifier capable
of operation below 144 MHz may be constructed
or modified during any calendar
year by an amateur operator for
use at a station without a grant of certification.